This invention relates to a process for the production of crystalline, thermoplastic, high density, low-pressure terpolymers of ethene, butene-1, and butene-2 by the polymerization of ethene in a liquid hydrocarbon phase containing butene-1 and butene-2 with a mixed catalyst of titanium trichloride and an organoaluminum compound.
The polymerization of ethene in C.sub.4 -cuts containing butene-1 and butene-2 with catalysts of titanium trichloride and chlorine-containing organoaluminum compounds is known, e.g., from DOS German unexamined laid-open application No. 2,214,271 and corresponding copending, commonly assigned U.S. Pat. No. 3,920,621 issued Nov. 18, 1975, the contents of which are incorporated by reference herein. However, in this process, no co- or terpolymers with butene-2 are obtained. According to another process described in German patent application No. P 23 50 065.4 and corresponding copending, commonly assigned U.S. patent application Ser. No. 511,130 filed Oct. 2, 1974, the contents of which are incorporated by reference herein, co- and terpolymers of ethylene, wherein likewise no butene-2 is incorporated, are obtained in C.sub.4 - and/or C.sub.3 /C.sub.4 -cuts which contain butene-2, with catalysts of titanium trichloride and trialkyl aluminum compounds.
The preparation of copolymers of ethene with 2-olefins has been described, e.g., in British Pat. No. 932,658, and the production of co- and terpolymers of ethene with 1-olefins and 2-olefins has also been disclosed, e.g., in British Pat. No. 967,788. According to these patents, co- and terpolymerization takes place with the aid of mixed catalysts of compounds of transition metals, e.g., the Ti, V, or Cr halides and/or the V or Cr acetylacetonates or V haloalcoholates with organometallic compounds of metals of group IA, II, or IIIA of the Periodic Table. The yields in this process, however, are extremely poor, in some instances even lower then the amounts of catalyst employed. Such processes are thus completely uninteresting from a technical viewpoint.